1. Field of the Invention
The present invention relates to a light source apparatus using an LED (Light-emitting Diode), a backlight apparatus equipped with the light source apparatus, a liquid crystal display apparatus equipped with the backlight apparatus, and a manufacturing method of the backlight apparatus.
2. Description of the Related Art
In the past, in an LCD (Liquid Crystal Display) mounted in an electronic apparatus such as a liquid crystal television, a PC (Personal Computer), or the like, an image has been displayed by placing a backlight on the back surface side of the LCD and illuminating the back surface of the LCD with the backlight. As a light source of this backlight, a CCFL (Cold Cathode Fluorescent Lighting) has been used in the past.
In recent years, an LED has been considered to be a hopeful light source to replace this CCFL. The use of the LED enables an increase in efficiency and an increase in color gamut and eliminates an adverse effect on the environment since unlike the CCFL, mercury is not used.
However, the LED generally varies in both chromaticity and luminance more widely than other light sources such as the above CCFL. Therefore, if the LED distributed in the marketplace is randomly used as the light source for the backlight, uniformities of both chromaticity and luminance become lower (uneven color and uneven luminance increase), and the yield of the backlight apparatus extremely deteriorates. Thus, the LED is not suitable for mass production.
As a technique to solve these problems of uneven color and uneven luminance, for example, Japanese Patent Application Laid-Open No. 2006-133708 (paragraph [0096], FIG. 15, etc.) discloses the following technique. That is, a light emitting diode unit formed with an aim to obtain a predetermined chromaticity and luminance using a plurality of light-emitting diodes having variations in chromaticity and luminance of emitted white light is used as a light source of a backlight apparatus. In this case, a plurality of light-emitting diode units of two types, main and sub types, which emit white lights having different chromaticities or luminances are arranged in columns such that sub light-emitting diode units are not arranged side by side on the same row. In addition, the sub light-emitting diode units arranged in the central column of a two-dimensional matrix are arranged on the central side of a liquid crystal panel. As a result, the occurrence of uneven color and uneven luminance of the whole backlight apparatus is prevented.
Further, Japanese Patent Application Laid-Open No. 2004-342608 (paragraph [0005], etc.) discloses a backlight illumination system. In the backlight illumination system, when a predetermined number of LED sets having different chromaticities are arranged on a straight line, respective LED sets having substantially the same chromaticity are arranged at substantially even intervals, so that uniform color as a whole can be obtained.
Furthermore, Japanese Patent Application Laid-Open No. 2005-332828 (paragraph [0024], etc.) discloses the following technique. That is, in arranging a plurality of LEDs in sequence, the respective LEDs are sorted according to their luminance levels, and the LED having a lower luminance is provided at a position corresponding to an end portion of an LCD, thereby attaining chromaticity uniformity of a backlight.